1 D 0 D 0 Quantum Correlations, Mixing, and Strong Phases Werner Sun, Cornell University for the CLEO-c Collaboration Particles and Nuclei International Conference October 2005, Santa Fe, NM Introduction and motivation Experimental technique Preliminary results and future plans

PANIC05, October 2005, Santa Fe, NMWerner Sun, Cornell University 2 Effect of Quantum Correlations  |D 1,2 > = p|D 0 > ± q|D 0 >  Because of quantum correlation between D 0 and D 0, not all final states allowed. This affects:  total rate  apparent branching fractions  Two entangled causes:  Interf. between CF and DCSD.  D mixing: single tag rates depend on y = B (CP+)  B (CP-).  Semileptonic decays tag flavor unambiguously (if no mixing)  If one D is SL, the other D decays as if isolated/incoherent.  Exploit coherence to probe DCSD and mixing—shows up in time- integrated rates. e  e    *  D 0 D 0 C =  1 KK KK KK KK KK KK KK K  l  CP+ K  l  CP- K  l  K  l  K  l  CP+CP- CP+ CP- interference forbidden by CP conservation forbidden in absence of mixing maximal constructive interference

PANIC05, October 2005, Santa Fe, NMWerner Sun, Cornell University 3 Introduction  In the Standard Model, D mixing strongly suppressed (CKM and GIM).  Previous searches:  Double semileptonic rates give R M.  Time-dependent K  : x and y rotated by   Current analysis:  Uses time-independent yields.  Sensitive to y at first order.  No sensitivity to p/q≠1; neglect CPV in decay.  References:  Goldhaber, Rosner: PRD 15, 1254 (1977).  Xing: PRD 55, 196 (1997).  Gronau, Grossman, Rosner: hep-ph/  Atwood, Petrov: PRD 71, (2005).  Asner, Sun: hep-ph/ Definition Current knowledge y (  2 -  1 )/2  = B (CP+)  B (CP-) ± x (M 2 -M 1 )/  sensitive to NP x’ < RMRM (x 2 +y 2 )/2< ~1 x r K  DCS-to-CF rel. amplitude ±  K  DCS-to-CF relative phase  (weak) + ? (strong) z 2cos  None w 2sin  None A  Bf rf zf Bf rf zf ~-0.01 w/ SU(3)

PANIC05, October 2005, Santa Fe, NMWerner Sun, Cornell University 4 Single and Double Tag Rates  Hadronic rates (flavored and CP eigenstates) depend on mixing/DCSD.  Semileptonic modes (r =  = 0) resolve mixing and DCSD.  Rate enhancement factors, to leading order in x, y and r 2 :  A comes from sum over recoil states.  With C=+1 D 0 D 0  at higher energy,  Can separate A and y.  Sensitivity to wx at first order. Not much info if w is small. fl+l+CP+CP- fR M /r 2 f1+r 2 (2-z 2 ) l-l-11 CP+1+rz10 CP-1-rz120 X1-rz( A -y)11+( A -y)1-( A -y) With C=-1, cannot separate y and A DD Single tag: X i DD Double tag: j i

PANIC05, October 2005, Santa Fe, NMWerner Sun, Cornell University 5 Experimental Technique  Use fitter from CLEO-c D absolute hadronic branching fraction analysis [ physics/ ].  Based on MARK III double tag technique using:  single tags ( n i ~ N DD B i  i ) and double tags ( n ij ~ N DD B i B j  ij )  281 pb -1 = 1.0 x 10 6 C=-1 D 0 D 0 pairs.  Limiting statistics: CP tags—our focus is not on B s.  Kinematics analogous to  (4S)  BB: identify D with   (M BC ) ~ 1.3 MeV, x2 with  0   (  E) ~ 7—10 MeV, x2 with  0  Procedure tested with CP-correlated MC. Modes f KK KK CP+ KKKK  K0S00K0S00 CP- K0S0K0S0 l X  e  X  e   ~ n/ 

PANIC05, October 2005, Santa Fe, NMWerner Sun, Cornell University 6 Hadronic Single Tags  Standard D reconstruction.  Cut on  E, fit M BC distribution to signal and background shapes.  Efficiencies from (uncorrelated) DD Monte Carlo simulations.  Peaking backgrounds for:  K  from K/  particle ID swap.  Modes with K 0 S from non-resonant     CP+ CP- f Mode  (%) % bkgSignal Yield (10 3 ) KK 65.7 ± ± 0.2 KK 66.7 ± ± 0.2 KKKK 58.9 ± ± 0.08  73.5 ± ± 0.12 K0S00K0S0 ± ± 0.17 K0S0K0S ± ± 0.11 M BC for K 0 S  0 (CP-) M BC for     (CP+) M BC for K    (f) Note log scale DATA (GeV)

PANIC05, October 2005, Santa Fe, NMWerner Sun, Cornell University 7 Hadronic Double Tags  Cut and count in M BC1 vs. M BC2 plane, define four sidebands.  Uncorrelated background: one D misreconstructed (sometimes both).  Signal/sideband scale factor: integrate background function from ST fits.  Mispartition background: particles mis-assigned between D 0 and D 0. Data KK KK KKKK  K0S00K0S00 K0S0K0S0 Yields 2.5 ± ± ± ± ± ± ± ± ± ± ± ± 9.5 KK 2.7 ± ± ± ± ± ± ± ± ± ± 8.8 KK 5.2 ± ± ± ± ± ± ± ± 6.3 KKKK 1.1 ± ± ± ± ± ± 3.7  1.2 ± ± ± ± 4.4 K0S00K0S00 9.7 ± ± 1.7 K0S0K0S0 No-QC expectation Observed in data M BC (K  K   vs. M BC (K 0 S  0 ) DATA (GeV)

PANIC05, October 2005, Santa Fe, NMWerner Sun, Cornell University 8 Inclusive Semileptonic Double Tags  Tag one side with K  or CP eigenstate, search for electron in remainder of event:  Fit electron spectrum for signal and background.   conversion,  0 Dalitz decay: charge symmetric.  Mis-ID: hadrons faking electrons.  Mis-tag: estimate from tag-side M BC -  E sideband.  Require right-sign electron charge for K  tag.  Efficiency correction in bins of p e. Tage  e (%) % bkgSignal Yield KK  ± 35 KK  ± 36 KKKK  ± 12 KKKK  ± 12   ± 9   ± 7 K0S00K0S00  ± 12 K0S00K0S00  ± 12 K0S0K0S0  ± 15 K0S0K0S0  ± 15 e  vs. K    e  vs. K 0 S  0  e vs. p e p e (GeV) in DATA

PANIC05, October 2005, Santa Fe, NMWerner Sun, Cornell University 9 Systematic Uncertainties  Mixing/DCS parameters determined from ST/DT double ratios:  Correlated systematics cancel (tracking/  0 /K 0 S efficiencies).  Different systematics from branching fraction measurements.  Uncorrelated systematic uncertainties included in the fit:  Yield fit variation.  Possible contribution from C=+1 initial state.  Can limit with CP+/CP+, CP-/CP- double tags—forbidden for C=-1.  Data provides self-calibration of initial state.  Signal yields have peaking backgrounds of opposite CP or flavor  bias in estimates from uncorrelated MC.  Possible bias from CP-correlated MC test.  Full systematic error analysis in progress.  Currently,  syst ~  stat.

PANIC05, October 2005, Santa Fe, NMWerner Sun, Cornell University 10 Results  Fit inputs: 6 ST, 14 hadronic DT, 10 semileptonic DT, efficiencies, crossfeeds, background branching fractions and efficiencies.   2 = 17.0 for 19 d.o.f. (C.L. = 59%). ParameterValuePDG or CLEO-c NDDNDD (1.09 ± 0.04 ± ?)x10 6 (1.01 ± 0.02)x10 6 A -y0.057 ± ± ? r2r ± ± ? (3.74 ± 0.18)x10 -3 PDG + Belle + FOCUS rz0.130 ± ± ? RMRM (1.74 ± 1.47 ± ?)x10 -3 < ~1x10 -3 B (K    ) (3.80 ± 0.29 ± ?)%(3.91 ± 0.12)% B(KK)B(KK)(0.357 ± ± ?)%(0.389 ± 0.012)% B()B() (0.125 ± ± ?)%(0.138 ± 0.005)% B(K0S00)B(K0S00) (0.932 ± ± ?)%(0.89 ± 0.41)% B(K0S0)B(K0S0) (1.27 ± 0.09 ± ?)%(1.55 ± 0.12)% B (X  e  ) (6.21 ± 0.42 ± ?)%(6.87 ± 0.28)% PRELIMINARY  Fitted r 2 unphysical. If constrain to WA, cos  = 1.08 ± 0.66 ± ?.  Limit on C=+1 contamination:  Fit each yield to sum of C=-1 & C=+1 contribs.  Include CP+/CP+ and CP-/CP- DTs in fit.  No significant shifts in fit parameters.  C=+1 fraction = 0.06 ± 0.05 ± ?.  Some branching fracs competitive with PDG. Uncertainties are statistical only

PANIC05, October 2005, Santa Fe, NMWerner Sun, Cornell University 11 Summary and Future Directions  With correlated D 0 D 0 system, can probe mixing and DCSD in time- integrated yields with double tagging technique.  Simultaneous fit for:  Hadronic/semileptonic/CP eigenstate branching fractions  Mixing and DCSD parameters.  Different systematics from previous measurements.  Method unique to threshold production—unavailable at Tevatron and B factories.  Add D 0  K 0 S     with Dalitz fits to increase CP eigenstate statistics.  Add wrong-sign e  vs. K    double tags to separate r and z.  Add C=+1 pairs from D 0 D 0  in √s ~4 GeV running to  separate A and y.  probe x.  Preliminary first measurements of  (K  ) and A -y.  Systematic uncertainties being studied.  Results affect other CLEO-c analyses.